Many hearing impaired individuals who are able to benefit from sound amplification utilize conventional air conduction hearing aids. However, a significant number of patients who could benefit from sound amplification are unable to utilize air conduction aids due to chronic inflammation or infection, as well as congenital or acquired malformation of the external ear canal and/or middle ear. For those patients that cannot be fitted with a conventional air conduction hearing aid, a bone conduction hearing device is sometimes recommended.
Bone conduction is a well known concept for sound amplification, dating back to the 16th century. Modern bone conduction hearing devices are available using either a steel headband or tight fitting eyeglass frames to press a sound transducer firmly against the patient's skull. The sound amplification electronics are mounted in a small "box" worn on the patient's clothing or within the eyeglass frames. There are, however, several disadvantages to this type of amplification. The soft tissues interposed between the sound transducer and the bone impair the direct transmission of sound to the bone, which can lead to distortion and poor sound fidelity. In addition, these devices of necessity generate a great deal of pressure against the soft tissue and the resultant discomfort and pain lead many patients to discontinue the use of the device.
A group of researchers in Sweden has attempted to accomplish this goal by anchoring a metal fixture in the patient's skull and routing this fixture through the skin (percutaneously) behind the ear. A bone conduction transducer is then fitted to the external projection of the fixture. This procedure raises serious concerns about the possibility of infection around the percutaneous connection and the possibility of patient injury in the event of trauma to the external projection of the bone fixture.
An improved hearing device component for subcutaneous attachment to the skull is described and claimed in copending application Ser. No. 674,176 filed Nov. 23, 1984, now abandoned, but continued under 35 USC 120 as application Ser. No. 737,188 filed May 23, 1985, now U.S. Pat. No. 4,612,915, granted Sept. 23, 1986.
It is an object of this invention to provide a method for implanting subcutaneously a hearing device component against the skull of a patient. It is still another object to provide a surgical kit for use in such an implantation procedure. Still other objects will appear in the more detailed description which follows.